If you want to use Binding you need to expose the usercontrol(s) as a DependencyProperty - Can access proprty in XAML or code behind.
AS an example you can expose the radiobutton as
public static readonly DependencyProperty Radio1Property = DependencyProperty.Register("Radio1", typeof(RadioButton),
typeof(YourUserContol),
new PropertyMetadata());
public RadioButton Radio1
{
get { return (RadioButton)this.GetValue(Radio1Property); }
set { this.SetValue(Radio1Property, value); }
}
or you can expose the controls as CLR-Public properties and you can then access in your code behind.
I hope this helps.